Beekeeping - Purdue Extension Entomology
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E-274-W
Beekeeping
Department of Entomology
PROTECTING HONEY BEES FROM PESTICIDES
Christian H. Krupke, Gregory Hunt and Rick E. Foster, Extension Entomologists
Honey bees are a vital part of our agricultural system, cause the bees to succumb to diseases. Remember that bees
as are many other species of pollinators. The annual value won’t encounter any of these mortality factors in isolation;
of honey bee pollination in the U.S. has been estimated at usually two or more are present at any given time. This is
$14.6 billion dollars. Although this (or any such estimate) is the main reason that working out a single “solution” to honey
approximate at best, the value of bee pollination is staggering. bee declines is an unrealistic expectation.
Honey is a secondary product that is quite important in its
own right. When Pesticide Poisoning May Occur
Honey bees are our key pollinator and saddled with a Bees consume pollen, nectar and water to survive. All are
range of challenges to colony health. Most bee researchers potential sources of pesticide exposure. In addition, bees may
believe that Varroa mites and the viruses that they transmit to be exposed to pesticides en route to collect these resources,
honey bees are the biggest single mortality factor for honey in dusts or liquids suspended in the air as they fly through
bees. Refer to “Mites of Honey Bees” for more information. attracted to a crop that is in bloom, or may be attracted into
Honey bees are also affected by diseases such as American treated crop fields by the presence of blooming weeds even
foulbrood, European foulbrood and dysentery, caused by a though the crop itself is not in bloom. Dandelion, wild mustard,
microsporidian parasite. Moving bee hives long distances white clover, yellow rocket, sweet clover, milkweed, goldenrod,
for pollination or to overwinter them in warmer climates can and aster blossoms all attract bees and are often present in
add stress, often resulting in up to 5% colony losses in a areas beside crop fields, ditches, or roadsides. Planting of
single move. Bees can also suffer from poor nutrition when corn and soybean seed, typically treated with neonicotinoid
few floral sources are available or when there is too much insecticides, can lead to bee kills as well when bees fly through
competition from other hives. In addition, pesticides are an the dust that arises during planting with pneumatic planting
ongoing concern and can kill bees outright or bees can receive equipment. Bees will sometimes forage in field crops when
sub-lethal doses that may reduce the colony population or these are producing pollen, including field corn and soybeans.
Social insects, such as honey bees, can quickly spread Honey bees often prefer stagnant pools for drinking water.
harmful organisms through the colony.
Protecting Honey Bees from Pesticides— E-53-W 2
When bees are killed by pesticides it is often because the
product drifted directly onto the bees or onto flowers that
the bees are feeding on. The recent popularity of systemic
insecticides, primary neonicotinoids, however, have led to
new exposure routes. Uptake of contaminated soil water by
both crop and non-crop plants is a new and important route
for exposure as well – many types of pollen from crops and
non-crops alike has been found to be contaminated with
pesticides. Contaminated water sources are also a culprit,
as bees seem to favor ponds, wheel ruts and mud puddles
for their drinking water.
Reducing the Hazard (Growers and Homeowners)
Pesticides are often over-applied because applications
are made prophylactically. Ensure that there is a pest problem
before applying any insecticide. If insecticides must be used, Finding dead honeybees does not always indicate a
several steps may be taken by the grower to reduce the haz- pesticide kill, check the symptoms of dying bees closely to
ard to bees. Avoid using dusts wherever possible. Dust may narrow down the cause.
be unavoidable in some cases, such as during the planting
of treated corn and soybean seeds – small amounts of these
chemicals mixed and forced into dust plumes by planters
is very highly toxic to bees. Use chemicals with reduced Reducing the Hazard (Beekeepers)
risk to bees whenever possible (see Tables below). Apply If a highly toxic insecticide to bees is to be used in an
insecticides in the late evening, night, or very early morning area of your hives, be prepared to take steps to reduce risk
when fewer bees will be foraging, and when spray drift and of poisoning. One of the most important steps in protecting
volatilization due to extreme heat are at a minimum. Do not your bees is the selection of an apiary location with low
spray when winds favor drifting, and use ground applications pesticide risk. This may not often be feasible, so be sure to
instead of air where possible. Avoid spraying when the crop notify growers and applicators in the area, the county exten-
or other plants in the field or nearby (including weeds) are in sion agent, and the State Apiary Inspector of the location of
bloom. Homeowners often use more pesticide (per unit area) your hives.
than agricultural producers and should consider minimizing Learn as much as you can about the chemical under
or eliminating pesticide use wherever possible. If you use consideration before making a decision on how to protect
systemic insecticides, such as neonicotinoids, in your lawn your bees. If the insecticide to be used has a long residual
or garden you may be inadvertently exposing bees to sub- life and is being applied to a plant where bees are foraging,
lethal concentrations of insecticide in flowers for a period of it may be best to move your bees out of the area. Remember
time well beyond the treatment date. Read the label (under that the new site must be at least 3 miles away to prevent
environmental statements) to see whether a product is toxic bees from returning to the old one. Make sure the new site
to bees or is systemic in the plant. is safe and notify the growers and applicators in that area
of your intentions. If the insecticide has a short residual life,
you may be able to confine your bees until the danger has
passed. Be sure the hive does not overheat if you choose
this method.
Community Communication and Cooperation
Many bee poisoning problems could be prevented by
better communication and cooperation among the grower,
pesticide applicator, and the beekeeper.
Because bees forage far beyond the colony, all beekeep-
ers within 2 to 3 miles of the area to be treated should be
notified at least the evening before the insecticide is to be
applied. If the beekeeper is to move or confine his bees, he
must do so the night before the treatment. Keep your hives
away from potential sources of pesticides. Corn planting has
been associated with honey bee mortality, so you may want
to screen off the entrances during planting time so that the
bees cannot fly. If you only have one or two hives you might
even turn on the water sprinkler to keep the bees at home –
Insecticides applied to the agricultural field could drift onto they will behave as if it is raining and not forage for the day,
the dandelions where honey bees forage. reducing their chances of exposure.
3 Protecting Honey Bees from Pesticides— E-53-W
Since many decisions to use an insecticide are made
only a few hours before the application is made, growers and
applicators should be aware of the location of all hives within
3 miles of their crops and know how to contact the beekeeper
who owns them. If this information is not available from a
resident of the area, local county extension personnel may be
of assistance. Most beekeepers register the location of their
hives with the State Apiary Inspector. Increasingly, beekeep-
ers are using the website located at http://www.fieldwatch.
com where there are resources for both beekeepers and crop
producers. The names of beekeepers in your area can also
be obtained by writing: State Apiary Inspector, Department
of Natural Resources, 420 W. Washington St., Indianapolis,
IN 46204, PH: 317-232-4120.
Diagnosing Unexpected Bee Kills Large numbers of dead and dying bees outside the hive
entrance is often due to encounter with pesticides.
Despite all of the safeguards outlined above, pesticide-
related bee kills do happen occasionally. A bee kill from pesti-
cides usually appears quickly. You may see many dead bees
in front of the hive one day that were not there the day before. having this essential first step performed promptly, you will
You may also see trembling bees because most insecticides be unable to document the cause of the mortality properly.
are nerve toxins. A pesticide kill can be confused with bee
mortality caused by Varroa mites, which usually occurs late in Classes of Pesticides
the summer or fall when mite populations are highest. When
this happens, bees are more vulnerable to viral infection and The type of pesticide and how bees are exposed deter-
may be seen dead in front of the hive or crawling and trembling mines the risk to bees. Their toxicity is measured by the LD50
in the grass. This is a more gradual, subtle process that usually (Lethal Dose, 50%), which is the dose that would kill half of the
occurs over a period of weeks (see below for more details). bees that contact the pesticide. There are a range of potential
A colony that dies as a result of Varroa mites may also just exposure routes (oral, contact are two common examples),
dwindle without the appearance of dead bees because the and bees are typically exposed to multiple pesticides at once.
sick bees do not return to the hive. This can even happen in Bees are insects, and most poisoning problems are attributed
early winter, refer to “Mites of Honey Bees” . If you suspect that gicides) may occasionally cause problems for bees. Be sure
your bees died from pesticide poisoning you should contact to read all labeling with any pesticide, especially any specific
the Office of Indiana State Chemist and make an incident report. Without pesticides and their properties please see the tables below.
Reference to products in this publication is not intended
to be an endorsement to the exclusion of others that may be
similar. Persons using such products assume responsibility for
Comparing and Contrasting Bee Kills Caused by Either their use in accordance with labeling. The categories below
Pesticides or Varroa Mites*. are not regulatory designations and are for information only.
Cause of Bee Pesticides Varroa Mites
Kill:
Timing of Kill: Anytime when Usually late in sea-
pesticide is ap- son
plied
Speed of Kill: Usually rapid Usually slow (over
(1-3 days) weeks)
Symptoms Trembling, Generally fewer,
uncoordinated scattered bees dead
movements, of- outside hive, may
ten large piles of also abandon hive
dead/dying bees
at hive
*Colony collapse caused by mites sometimes will show a few
bees with deformed wings.
Protecting Honey Bees from Pesticides— E-53-W 4
Table 1. Highly Toxic Pesticides. This group includes materials that kill bees on contact during application and
for one or more days after treatment. Bees should be moved from the area if highly toxic materials are used on
plants the bees are visiting.
Pesticides by Common Name Pesticides by Trade Name
abamectin (Agri-Mek, Avid) Actara, Platinum, FarMore (thiamethoxam)
acephate (Orthene, Address) Admire Pro (imidacloprid)
bifenthrin (Capture, Brigade) Agri-Mek (abamectin)
carbaryl (Sevin) Ambush, Pounce (permethrin)
carbofuran (Furadan) Ammo (cypermethrin)
chlorpyrifos (Dursban, Lorsban) Apollo (clofentezine)
chlorethoxyfos (Fortress) Asana (esfenvalerate)
clofentezine (Apollo) Avid (abamectin)
clothianidin (Belay, Poncho seed treatment) Baythroid (cyfluthrin)
cyfluthrin (Baythroid) Belay (clothianidin)
cyhalothrin (Warrior) Capture, Brigade (bifenthrin)
cypermethrin (Ammo) Cruiser seed treatment (thiamethoxam)
deltamethrin ( Delta Gold) Cygon, Dimethoate (dimethoate)
diazinon (Diazinon, Sprectracide) DDVP (dichlorvos)
dichlorvos (DDVP) Delta Gold (Deltamethrin)
dimethoate (Cygon, Dimethoate) Delegate/Radiant (spinetoram)
emamectin (Proclaim) Diazinon (diazinon)
esfenvalerate (Asana) Dibrom (naled)
fenpropathrin (Danitol) Lorsban (chlorpyrifos)
hexythiazox (Savey/Onager) Envidor (spirodiclofen)
imidacloprid (Admire Pro) Fortress (chlorethoxyfos)
indoxacarb (Avaunt) Fury, Mustang (zeta-cypermethrin)
malathion (Cythion), low volume Imidan (phosmet)
methamidophos (Monitor) Lannate (methomyl)
methidathion (Supracide) Mesurol (methiocarb)
methiocarb (Mesurol) Monitor (methamidophos)
methomyl (Lannate) Movento (spirotetramet)
naled (Dibrom) Nexter (pyridaben)
novaluron (Rimon) Orthene (acephate)
permethrin (Ambush, Pounce) Poncho seed treatment (clothianidin)
phosmet (Imidan) Proaxis (gamma-cyhalothrin)
pyridaben (Nexter) Proclaim (emamectin)
spinosad (Tracer) Rimon (novaluron)
spinetoram (Delegate/Radiant) Savey, Onager (hexythiazox)
spirodiclofen (Envidor) Sevin (carbaryl)
spirotetramet (Movento) Spectracide (diazinon)
thiamethoxam (Cruiser, Actara, Platinum, FarMore) Supracide (methidathion)
zeta-cypermethrin (Fury, Mustang) Tracer (spinosad)
Warrior (lambda-cyhalothrin)
5 Protecting Honey Bees from Pesticides— E-53-W
Table 2. Moderately Toxic Pesticides. These materials can be used with limited danger to bees if not applied
over bees in the field or the hives. Correct dosage, timing, and method of application are essential. This group
includes:
Pesticides by Common Name Pesticides by Trade Name
acetamiprid (Assail) Acramite (bifenazate)
bifenazate (Acramite) Assail (acetamiprid)
carbaryl (Sevin XLR formulation only) Calypso (thiacloprid)
ethoprop (Mocap) Confirm (methoxyfenozide)
malathion (Malathion) Counter (terbufos)
methoxyfenozide (Confirm) Entrust (spinosad)
oxamy (Vydate) Esteem (pyriproxyfen)
phorate (Thimet) Larvin (thiodicarb)
pyriproxyfen (Esteem) Malathion (malathion)
spinosad (Entrust) Mocap (ethoprop)
spiromesifen (Oberon) Oberon (spiromesifen)
terbufos (Counter) Sevin XLR (a specific carbaryl formulation)
thiodicarb (Larvin) Thimet (phorate)
Vydate (oxamyl)
Table 3. Relatively Nontoxic Pesticides. Materials in this group can be used with few precautions and a mini-
mum of injury to bees. Fungicides are indicated by an “F”. The largest number of materials are in this group
which includes, but is not limited to:
Pesticides by Common Name Pesticides by Trade Name
allethrin (Pynamin) Altacor/Coragen (chlorantraniliprole)
amitraz (Mitac) Beleaf (flonicamid)
azadirachtin (Neemix, Align) Belt (flubendiamide)
Bacillus thurgingiensis or Bt (Biobit, DiPel, Full-Bac, Javelin, Biobit (Bacillus thuringiensis)
MVP, etc.)
Bordeaux mixture - F Bordeaux mixture - F
captan - F Captan - F
chlorantraniliprole (Altacor/Coragen) Confirm (tebufenozide)
chlorothalonil (Bravo) - F Dimilin (diflubenzuron)
copper compounds (Kocide) - F Dipel (Bacillus thuringiensis)
cyromazine (Trigard) Dithane (zineb) - F
dicofol (Kelthane) Dithane M-22 (maneb) - F
diflubenzuron (Dimilin) Dithane M-45 (mancozeb)
etoxazole (Zeal) Dylox (trichlorfon)
fenpyroximate (Portal) Fulfill (pymetrozine)
flonicamid (Beleaf) Full-Bac (Bacillus thuringiensis)
flubendiamide (Belt) Javelin (Bacillus thuringiensis)
fluvalinate (Spur) Kelthane (dicofol)
koalin (Surround) Kocide (copper compounds) - F
mancozeb (Dithane M-45) - F MVP (bacillus thuringiensis)
maneb (Dithane M-22) - F Neemix, Align (azadirachtin)
metiram (Polyram) - FProtecting Honey Bees from Pesticides— E-53-W
6
Table 3 (Con’t). Relatively Nontoxic Pesticides. Materials in this group can be used with few precautions and
a minimum of injury to bees. Fungicides are indicated by an “F”. The largest number of materials are in this
group which includes, but is not limited to:
Pesticides by Common Name Pesticides by Trade Name
pymetrozine (Fulfill) Omite (propargite)
pyrethrum (nature) Polyram (metiram) - F
sulfur - F Portal (fenpyroximate)
tebufenozide (Confirm) Pynamin (allethrin)
trichlorfon (Dylox) Spur (fluvalinate)
zineb (Dithane) Sulfur - F
Surround (kaolin)
Trigard (cyromazine)
Zeal (etoxazole)
READ AND FOLLOW ALL LABEL INSTRUCTIONS. THIS INCLUDES DIRECTIONS FOR USE, PRECAUTIONARY STATEMENTS (HAZARDS TO HUMANS, DOMESTIC ANIMALS, AND ENDANGERED
SPECIES), ENVIRONMENTAL HAZARDS, RATES OF APPLICATION, NUMBER OF APPLICATIONS, REENTRY INTERVALS, HARVEST RESTRICTIONS, STORAGE AND DISPOSAL, AND ANY SPECIFIC
WARNINGS AND/OR PRECAUTIONS FOR SAFE HANDLING OF THE PESTICIDE.
May 2021
It is the policy of the Purdue University Cooperative Extension Service that all persons have equal opportunity and access to its educational programs, services, activities, and
facilities without regard to race, religion, color, sex, age, national origin or ancestry, marital status, parental status, sexual orientation, disability or status as a veteran. Purdue
University is an Affirmative Action institution. This material may be available in alternative formats.
This work is supported in part by Extension Implementation Grant 2017-70006-27140/ IND011460G4-1013877 from the USDA National Institute of Food and Agriculture.
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